1. Field of the Invention
The invention relates to an element of a drum-shaped pulverizing apparatus, for example, for use in a gas-throughflow pulverizing machine with a rotating impact wheel system having an alternating arrangement of sections, with and without shaping, in the rotational direction, whereby the shaping is comprised of shaping ridges oriented adjacent one another, with recesses lying between the shaping ridges, and the shaping ridges are sloped at an angle oppositely with respect to the symmetry axis that is oriented in the direction of rotation.
2. Background of the Invention
Elements of the type described above are especially known in connection with grinding containers. These elements, in their circumferential alignment with respect to one another, form the surface of the grinding container on which the coarse feed material is transformed into fine material. The desired degree of fineness for the fine material is determined, in this connection, by the envisioned range of application of the fine material.
The degree of fineness depends on several factors such as, for example, the distance of the impact wheel from the surface of the grinding container or the cross-sectional makeup of the shaping arrangement, especially as regards the length of time that the coarse material is held in the grinding container. The holding time encompasses the elapsed time from the initial introduction of the coarse material into the grinding container until the grinding container is emptied.
The holding time can be influenced by predetermined measures relating to the impact wheel, as discussed, for example, in DE 198 35 144 A1. The holding time can also be controlled, however, by the manner in which the shaping arrangement is oriented on the surface of the grinding container. For this purpose, it is known to orient the shaping ridges in the form of a xe2x80x9cVxe2x80x9d with respect to the grinding apparatus surface. Consequently, a short or long holding time (of the feed material in the grinding container) prevail, depending on whether the shaping ridges are open or closed in the circumferential direction of the impact wheel.
An objective in connection with pulverizing coarse material is always to obtain a maximal amount of optimally sorted fine material. In other words, the variation in the degree of fineness, both in size and shape, is to be kept as low as possible.
In known apparatus, individual sections with a shaped surface are positioned one after the other in the circumferential direction of the impact wheel, with the interposition of non-shaped sections. In this connection, the influence borne by shaping a given section, in connection with the shaping of a subsequent section, on the flow of material inside the pulverizing apparatus, warrants no consideration. In this manner, it is possible to observe in existing pulverizing apparatus that neither the shaping ridges nor the recesses (of a given section or of an element having a similar section) lying therebetween will align. In other words, between the shaping arrangements of two neighboring sections or elements a more or less starkly defined shift exists via which, during operation of such a pulverizing machine, the holding times of the coarse material in the grinding container will fluctuate much too an excessively. A portion of the coarse material will quickly progress through the shaped sections of the grinding container in a straight shot so that the result will be fine material with coarse grains. Another portion, when progressing through, will hit the grinding surfaces at the rear side of the shaping ridges of the subsequent shaped section and will then always be stopped and turned back so that, because of the long holding time that results, some fine material of reduced diameter will be produced.
The great range of variation, in the size and shape of fine material product, caused by the above will reduce the quality of the fine material and, in some cases, will necessitate a further sifting of the fine material.
In the context discussed above, the object of the invention is to control the degree of fineness of the fine material via the type of shaping arrangement employed by the elements in the pulverizing apparatus and, at the same time, to produce, in abundance, optimally sorted fine material.
In accordance with the invention, this object is achieved by way of an element having the following features: the shaping ridges of a shaped section are aligned either with the shaping ridges, or the recesses between shaping ridges of a subsequent shaped section.
Advantageous modifications are set forth throughout the instant disclosure.
A fundamental concept of the present invention is to bring the individual shaped sections, of a pulverizing apparatus that is configured to achieve a given result, into association with one another and to harmonize them with one another. In this connection, the goal is to create to most uniform flow ratios as far as the material flow in the grinding container is concerned, that is, the passage of the coarse material within the grinding container will not overcome contingencies but will, by way of constructive measures, be predeterminable.
In this connection, control of the holding time of the coarse material within the pulverizing apparatus can be achieved as well as control of the degree of fineness. Moreover, the result will be optimally sorted fine material that is also qualitatively of great value and that can be used for further processing without first being finishprocessed.
By way of an advantageous embodiment, the length of the element side disposed at the circumference of the pulverizing apparatus is equivalent to {fraction (1/10)} to {fraction (1/30)} the circumference of the pulverizing apparatus. With the largest possible elements, the number of elements provided in a complete pulverizing apparatus will be as small as possible, with the result that the time expenditure associated with the installation and removal of the individual elements will be minimal. For a given size of the elements, they must (in terms of their cross-section) be able to accommodate to the curve of the pulverizing apparatus. Otherwise, an effective pulverization of the coarse material cannot be guaranteed, on account of deviations from the rotational track of the impact wheel.
According to another advantageous embodiment of the invention, the lengths of the sides of the shaped sections disposed at the circumference of the pulverizing apparatus vary in the range from 20 to 30 mm. With smaller dimensions for the sections, the quantity of sections will correspondingly increase. With a shifted alignment of the shaping arrangement with respect to a subsequent section, the result is a frequent stoppage and deflection of the material flow as in the case of large elements so that, in this manner, the holding time of the coarse material can be increased considerably. At the same time, the number of edges extending transversely with respect to the direction of rotation, and that define the borders of the sections, will also be increased. These edges undertake a significant portion of the pulverizing activity so that, with an increase in the number of edges, the efficiency of the pulverizing apparatus will also ultimately increase.
Further, it is advantageous to provide more shaped sections, inclusive of non-shaped sections disposed therebetween, on an element. In this connection, the desired orientation and harmonization of the shaping arrangement, with respect to sections disposed one after the other, is easily achieved and thus no longer constitutes any source of error when the elements are mounted. As far as large elements are concerned, it is also the case that expenditures relating to installation are reduced.
Further advantages are realized with the shaping ridges being oriented at an angle that is 25xc2x0 to 45xc2x0 with respect to the symmetry axis (of the elements) oriented in the direction of rotation. With an acute angle of impact of the coarse material on the shaping ridges, the impact energy, and the associated abrasion on the element, is reduced. In addition, because of the greater length of the shaping ridges, the result is a longer holding time of the coarse material within the grinding container, which leads to a higher degree of fineness.
A further advantageous embodiment is provided when the width of the shaping ridges is greater than that of the recesses between the shaping ridges. With a shifted orientation of the shaping arrangement, it is thus guaranteed that the entire quantity of coarse material will be stopped and deflected between two shaped sections.
As discussed herebelow, further constructive measures are contemplated in connection with suitably shaped surfaces of an element according to the invention, whereby the desired degree of fineness can be achieved.